Anapole states - characterized by a strong suppression of far-field scattering - naturally arise in high-index nanoparticles as a result of the interference between certain multipolar moments. Recently, the first-order electric anapole, resulting from the interference between the electric and toroidal dipoles, was characterized under in-plane illumination as required in on-chip photonics. Here, we go a step further and report on the observation of higher-order (magnetic and second-order electric) anapole states in individual silicon disks under in-plane illumination. To do so, we increase the disk dimensions (radius and thickness) so that such anapoles occur at telecom wavelengths. Experiments show dips in the far-field scattering perpendicular to the disk plane at the expected wavelengths and the selected polarizations, which we interpret as a signature of high-order anapoles. Some differences between normal and in-plane excitation are discussed, in particular the non-cancellation of the sum of the Cartesian electric and toroidal moments for in-plane incidence. Our results pave the way towards the use of different anapole states in photonic integrated circuits, either on silicon or other high-index dielectric materials.
Detection of Hybrid Optical Anapoles in Dielectric Microspheres
Illinois State University（伊利诺伊州立大学）；Centro de Física de Materiales (CFM-MPC) CSIC-UPV/EHU（材料物理中心 (CFM-MPC) 西班牙科学研究中心-巴斯克国立大学）；Universidad de La Laguna（拉帕拉古纳大学）；Universidad Complutense de Madrid（马德里康普顿斯大学）
Tailored multipolar optical trapping with higher-order structured light
The Institute of Optics, University of Rochester（罗切斯特大学光学研究所）；Department of Physics, University of Rochester（罗切斯特大学物理系）；Center for Coherence and Quantum Optics, University of Rochester（罗切斯特大学相干与量子光学中心）
